Spontaneous Germinal Activation of Quiescent Uq Transposable Elements in Zea Mays L

The spontaneous germinal activation of quiescent Uq transposable elements is reported. Thirty-nine spotted exceptions were observed at a rate of about 2 x 10(-4) from 687 otherwise colorless ears produced from the cross of a-ruq/a-ruq (colorless or occasionally sectored) X an a-ruq tester (colorless). All exceptions had spotting patterns distinct from the pattern of our original standard Uq (Uq1)-a-ruq spotting. From these spotted exceptions five new Uq elements (Uq2, Uq3, Uq4, Uq5 and Uq6) have been isolated. Genetic evidence for the Uq nature of the five germinal isolates is presented. First, each of the five spotted exceptions was homozygous for the a-ruq reporter allele. Second, four new Uq isolates (Uq2, Uq3, Uq4 and Uq5), after being reconstituted into a alpha degrees sh2/alpha degrees sh2 (no Uq) line, could transactivate the standard a-ruq allele and continue to produce their distinct spotting phenotypes. Third, these five new Uqs are also capable of transactivating the c-ruq65 and c-ruq67 alleles. However, the transactivation of c-ruq is generally weaker than that of a-ruq.     

Differentiation-related regulation of 1,25 dihydroxy vitamin D3 receptor mRNA in human leukaemia cells HL-60

Vitamin D receptor (VDR) is a nuclear protein which mediates the physiological actions of its hormone ligand, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). While it appears that the receptor-hormone complex regulates the expression of hormone-dependent genes involved in mineral homeostasis, its role in induction of differentiation of leukaemic cells is less clear. We have studied the expression of the VDR gene in several sublines of HL-60 leukaemic cells with varying responsiveness to 1,25(OH)2D3. Sublines which rapidly differentiated to monocytic forms were shown to contain elevated steady-state levels of VDR mRNA within 1 h of exposure to high concentration of 1,25(OH)2D3. This up-regulation of the expression of VDR was not apparent in sublines in which monocytic differentiation occurred after a delay of several days. Beginning at approximately 3 h after exposure to 1,25(OH)2D3 in most cases, there was a gradual decline in VDR mRNA levels. Measurement of steady-state levels of mRNA for c-myc and c-fos showed that in sublines of HL-60 cells which respond rapidly to 1,25(OH)2D3, elevation of VDR mRNA is evident prior to the changes in proto-oncogene expression. These data are consistent with the hypothesis that a change in VDR gene expression is one of the steps that promote monocytic differentiation.     

ph1b基因在Aegilops有益基因直接遗传转移中利用的可能性

第一次用中国春和中国春ph1b突变体对(中国春phlb突变体×Ae.uariabilis)F_1和(中国春ph1b突变体×Ae.turcomenica)F_1回交获得了成功,并通过连续回交,把Ae.turcomenica的抗白粉基因转移到了普通小麦中。证实了利用ph1b基因从山羊草属的一些种“直接遗传转移”有益基因到普通小麦中的可能性。     

350m氦氧模拟饱和潜水过程中潜水员坐位踏车时心缩间期的变化

在350m氦氧模拟饱和潜水过程中,对4名男性潜水员采用耳密度图导数图方法观察坐位踏车时心缩间期变化。在压力(300、230、135m)下和减压后的主要变化是等容收缩期、射血前期(PEP)和PEP/左室射血时间加大,与加压前比较有显著差异,尤其在踏车负荷加重时更为明显。提示心肌收缩力受高气压的影响而降低。     

甲肝病毒在人血白细胞中体外连续传代和在分类白细胞中增殖的研究

1985年我们采用间接免疫荧光法(IF法)检测出甲肝患者外周血白细胞中有甲肝抗原(HAAg)存在,继而又将HAAg阳性白细胞直接种入PLC/PRF/5细胞,分离到两株甲肝病毒(HAV)NJ—3株和H—1株。为了弄清白细胞所携带的病毒究竟仅为吸附吞饮,抑或能在其中复制增殖,我们将分离到的HAV用正常人血白细胞进行体外增殖试验,现将结果报告如下。     

小鼠肝脏金属硫蛋白Metallothioneins的分离纯化与鉴定

由健康小鼠通过皮下注射一定量的氯化镉,取肝脏匀浆,离心,经SephadexG-50和DEAE-Sephadex A-50柱层析分离,即可获得MT-Ⅰ和MT-Ⅱ两种金属硫蛋白。经鉴定:两个分子各含18个巯基,结合4个Cd原子和3个Zn原子,无金属蛋白质Thionein的分子量约为6kD,半胱氨酸含量约占氨基酸总量的28％,所提取到的MT-Ⅰ和MT-Ⅱ经氨基酸组成,HPLC和PAGE分析皆证明为高度均一的,且与有关文献报道基本相符。其中MT-Ⅱ已获得晶体。     

Isolation, expression, and mutation of a rabbit skeletal muscle cDNA clone for troponin I. The role of the NH2 terminus of fast skeletal muscle troponin I in its biological activity.

A cDNA for rabbit fast skeletal muscle troponin I (TnI) was isolated and sequenced. The clone contains a coding sequence predicting a 182-amino-acid protein with a molecular mass of 21,162 daltons. The translated sequence is different from that reported by Wilkinson and Grand (Wilkinson, J. M., and Grand, R. J. A. (1978) Nature 271, 31-35) in that Arg-153, Asp-154, and Leu-155 must be inserted into their original sequence. Amino acid sequencing of adult rabbit TnI confirmed this result. In order to investigate the role of the NH2 terminus of TnI in its biological activity, we have expressed a recombinant deletion mutant (TnId57), which lacks residues 1-57, in a bacterial expression system. Both wild type TnI (WTnI) and TnId57 inhibited acto-S1-ATPase activity and this inhibition could be fully reversed by troponin C (TnC) in the presence of Ca2+. Additionally both WTnI and TnId57 bound to an actin affinity column. Thus, both inhibitory actin binding and Ca(2+)-dependent neutralization by TnC were retained in TnId57. TnC affinity chromatography was used to compare the binding of TnI and TnId57 to TnC. Using this method, two types of interaction between TnC and TnI were observed: 1) one which is metal independent (or structural) and 2) one dependent on Ca2+ or Mg2+ binding to the Ca(2+)-Mg2+ sites of TnC. The same experiments with TnId57 demonstrated that the type 1 interaction was weakened, and type 2 binding was lost. This method also revealed an interaction between TnC and TnI which is dependent upon Ca2+ binding to the Ca(2+)-specific sites of TnC and which is retained in TnId57. Taken together, these results suggest that the NH2 terminus of TnI may constitute a Ca(2+)-Mg(2+)-dependent interaction site between TnC and TnI and play, in part, a structural role in maintaining the stability of the troponin complex while the COOH terminus of TnI contains a Ca(2+)-specific site-dependent interaction site for TnC as well as the previously demonstrated Ca(2+)-sensitive inhibitory and actin binding activities.     

Ligation activity of FLP recombinase. The strand ligation activity of a site-specific recombinase using an activated DNA substrate.

The FLP protein of the 2-microns plasmid of yeast belongs to the integrase family of site-specific recombinases whose members form a covalent bond between a conserved tyrosine of the recombinase and the 3'-phosphoryl group at the site of cleavage. We have made an activated DNA substrate and have shown that FLP can promote efficient strand ligation without forming a covalent intermediate with the DNA substrate. The strand ligation activity of FLP is independent of its ability to cleave DNA. Since site-specific recombinases are members of the larger class of topoisomerases, these findings may be generally applicable to other members of this class of enzymes.     

Physiological aspects of l-lysine production: effect of nutritional limitations on a producing strain of Corynebacterium glutamicum

The effect of nutritional limitations, such as phosphorus and carbon, on the production of l-lysine by Corynebacterium glutamicum was studied in continuous culture. We observed that phosphate-limited cultures at low growth rates were favourable to l-lysine production. l-Lysine was produced when a culture at low dilution rate (0.03 h^–1) was established. A dilution rate of about 0.04 h^–1 should be maintained in order to assure good productivity and an l-lysine yield of 0.53 g/g. Under carbon-limiting conditions the maintenance energy and growth yield of 0.03 g/g·g^–1·h^–1 and 0.41 g/g, respectively, have been obtained. Under these limiting conditions the l-lysine production was not favoured even at lower dilution rates.Correspondence to: N. Coello